[/color I have an AVIC D3 one 10" JL speaker in a PaoBox (I wanted more than one but my 2006 4 door F150 pickup didn't have enough room under the seat for more than one). I have had the speaker replaced three times so far. The guy I bought the system for just exchanges it out for another one but I would prefer to find the problem and correct it so that I don't have to replace it every 4-6 months. Any advice? Thanks!

You are either overpowering the subwoofer, or if it's a very small sealed type box the speaker may have too much travel and is ripping itself apart trying to compress the air inside the box, or possibly the cone/surround is actually hitting something when it's in operation.